SYMPTOMSWhen installing an amplifier in a vehicle how can you calculate what the maximum current draw will be on the vehicle's electrical system? The manual for the amplifer does not specify the maximum current draw

CAUSEIt is important to know the total current draw of any system being installed. This can help determine what gauge power and ground wire to use, what size fuse to use and if the vehicle's electrical system is up to the task of powering the complete system

RESOLUTIONYou will need 3 pieces of information to properly estimate the maximum current draw of an amplifier. These include the total rated maximum output of the amplifer at the load being presented, the system voltage (usually 12 volts) and the effeciency of the amplifier.
Ohms Law tells us that power divided by the system voltage will equal the current draw. P/E=I. This would be extremely easy if amplifiers were 100% effecient but that amplifier doesn't exist and probably never will. For an accurate estimate you must take into account the effeciency of the amplifier which gives an indication of how much input power is converted into output power suitable to drive a loudspeaker with the rest being dissipated as heat.
For an example we'll use an amplifier that is rated to deliver 200 watts total power at 4 ohms and is 50% effecient. This means that in order for the amplifier to produce 200 watts of power that same amount of power will be dissipated as heat. This tells us that in order for the amplifier to produce 200 watts of output power and the equivalent of 200 watts of dissipated heat it will need 400 watts of input power.
400 watts of input power divided by the system voltage of 12 volts gives us a current draw estimate of about 33 amps.

IMPORTANT NOTEThis article requires an advanced understanding of the installed system. Please contact your local Authorized Directed Dealer or Retailer if you require additional assistance.